Solid-state imaging apparatus or imaging readers, that have been configured either as handheld, portable scanners and/or stand-mounted, stationary scanners each having a presentation window, or as vertical slot scanners each having a generally vertically arranged, upright window, or as flat-bed or horizontal slot scanners each having a generally horizontally arranged window, or as bi-optical, dual window scanners each having both generally horizontally and vertically arranged windows, have been used in many venues, such as supermarkets, department stores, and other kinds of retailers, libraries, parcel deliveries, as well as factories, warehouses and other kinds of industrial settings, for many years, in both handheld and hands-free modes of operation, to electro-optically read by image capture a plurality of symbol targets, such as one-dimensional symbols, particularly Universal Product Code (UPC) bar code symbols, and two-dimensional symbols, as well as non-symbol targets, such as driver's licenses, receipts, signatures, etc., the targets being associated with, or borne by, objects or products to be processed by the imaging readers. In the handheld mode, a user, such as an operator or a customer, held the imaging reader and manually aimed a window thereon at the target. In the hands-free mode, the user slid or swiped a product associated with, or bearing, the target in a moving direction across and past a respective window in a swipe mode, or momentarily presented the target associated with, or borne by, the product to an approximate central region of the respective window, and steadily momentarily held the target in front of the respective window, in a presentation mode. The choice depended on the type of the reader, or on the user's preference, or on the layout of the venue, or on the type of the product and target.
The imaging reader included a solid-state imager (also known as an imaging sensor) with a sensor array of photocells or light sensors (also known as pixels), which corresponded to image elements or pixels over a field of view of the imaging sensor, and an imaging lens assembly for capturing return light scattered and/or reflected from a target being imaged over a working range of distances, and for projecting the return light onto the imaging sensor to initiate capture of an image of the target as pixel data. The imaging sensor was configured as a one- or two-dimensional charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) device, and included associated circuits for producing and processing an electrical signal corresponding to a one- or two-dimensional array of the pixel data over the field of view. The imaging sensor was controlled by a controller or programmed microprocessor that was operative for processing the electrical signal into data indicative of the target being imaged and, when the target was a symbol, for processing and decoding the symbol.
The known imaging lens assembly typically comprised a plurality of lenses of different sizes and optical powers. The lenses were made of glass or plastic, were held in a lens holder and were arranged along an optical axis. Since glass, as compared to plastic, had a relatively lower coefficient of thermal expansion and a relatively lower refractive index variation over temperature, it was sometimes preferred to make each lens of glass, rather than plastic, especially when it was desired to minimize focal shift over a wide operating temperature range. At other times, e.g., when the thermal instability and focal shift were not so critical in a particular application, it was preferred to make each lens of plastic, because a plastic lens is lighter than a corresponding glass lens and can be more easily and more inexpensively fabricated by molding, rather than machining and polishing. At still other times, a part-plastic, part-glass, hybrid lens design, in which at least one of the lenses was made of glass, e.g., for thermal stability, and at least another of the lenses was made of plastic, e.g., for lighter weight and ease of manufacture, was preferred to achieve the advantages of both glass and plastic.
The known imaging lens assembly also typically comprised an aperture stop having a rotationally symmetrical aperture, e.g., a circular aperture, on the optical axis. Alignment between the circular aperture and the imaging sensor was not critical, because the angular orientation of the circular aperture about the optical axis did not adversely affect optical imaging performance. However, in some applications, a non-rotationally symmetrical (or asymmetrical) aperture, e.g., a rectangular or elliptical aperture, was desired for an improved signal-to-noise ratio of the electrical signal, an extended range of the working distances, and a more reliable and responsive imaging reader performance, especially when using a one-dimensional, linear imaging sensor. In that event, the non-rotationally symmetrical aperture needed to be aligned with the linear imaging sensor. Specifically, the longer dimension of the non-rotationally symmetrical aperture needed to be positioned so that it extended along a direction generally perpendicular to the elongation of the linear imaging sensor. However, the known imaging lens assembly provided very little design flexibility in implementing such alignment between the non-rotationally symmetrical aperture and the linear imaging sensor. Without such alignment, the optical imaging performance characteristics of the imaging lens assembly were not fully realized.
Accordingly, it would be desirable to facilitate alignment between a non-rotationally symmetrical aperture of an imaging lens assembly and an imaging sensor, especially a linear imaging sensor, without sacrificing optical imaging performance.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.